Hoya 77mm PL-CIR HRT

Hoya 77mm PL-CIR HRT

Sunlight is naturally partially polarised by reflection from electrons in air molecules, which scatters the light and creates haze. A filter with polarising properties orders and filters this directionally polarised light perpendicular to the reflected light, absorbing a large part of it. This results in a noticeable reduction of glare and reflections from non-metallic surfaces and increased saturation of sky and foliage.

A circular polarisation filter differs from a linear polarisation filter in that, in addition to the linear polarising filter, it also contains a quarter-wavelength filter. This quarter-wavelength filter serves to circularly polarise the linearly polarised light for use with autofocus and exposure functions. Due to the way light is refracted and filtered by a linear polariser, autofocus and exposure accuracy are disrupted during use. When the light is circularly polarised, these functions can still be used.

This filter is uncoated and offers an average light transmission of around 98% thanks to the high-transparency polarising film. It is made from optical glass and precisely machined aluminium frames.